Document node: scheme

[Jamesernator]

Since at least Node 14 one can import builtin modules using the nodejs: scheme. e.g. import fs from "nodejs:fs"; or import("nodejs:fs"). However this capability doesn't seem to be documented anywhere (particularly not on the esm docs).

It would be good to either document this, if it is officially supported, or to warn when nodejs: scheme is used (if it's only for internal use).

[bmeck]

@Jamesernator that isn't stable and actually has been a discussion on if it should be node: since that is what policies use. Whenever we converge it will be documented

[bmeck]

nodejs/node#35387 has landed so the features have unified on node:, do we want to officially document this now? We have a semi-implicit documentation bit in the resolver spec already.

[bmeck]

made a PR to docs

[bmeck]

this has landed